1. Field of the Invention
The present invention relates to a check valve provided in a channel to prevent backflow of fluid from occurring, a fluid device including the check valve housed in a valve chamber, and a pump including the check valve and the valve chamber in a channel communicating with a pump chamber.
2. Description of the Related Art
A piezoelectric pump is used as a fuel transport pump for a fuel cell. The piezoelectric pump pumps fluid in a pump chamber by vibrating a diaphragm with a piezoelectric vibrator. A channel communicating with the pump chamber is provided with a check valve that prevents backflow of fluid from occurring (see, for example, Japanese Unexamined Patent Application Publication No. 2-245482). The check valve includes a support portion and a flexible portion. When pumping is performed while an inflow pressure is less than an outflow pressure and when pumping is stopped, the flexible portion closes the channel. Also, when pumping is performed while the inflow pressure is greater than the outflow pressure, the flexible portion is bent and causes the channel to be open.
In the channel provided with the check valve, when an unexpected change occurs during pumping the fluid, the flexible portion of the check valve may be bent to a greater extent than a predetermined level. For example, when a liquid having bubbles is pumped, the bubbles that are compressed at a high pressure are expanded because the pressure is released when the liquid passes the check valve. The flexible portion of the check valve may be bent to a large extent by the force of the expansion. Also, when high-pressure gas passes the check valve after the liquid is pumped, the flexible portion of the check valve may be bent to a large extent.
The flexible portion of the check valve can be restored even if the flexible portion is bent to a certain level. However, if the flexible portion is bent to a greater extent than the predetermined level, in some cases, the flexible portion may stick to a wall and close the channel at an abnormal position that is different from a normal position, at which the check valve normally closes the channel. For example, when a check valve made of silicone rubber is used, when fluid such as methanol is pumped, the surface of the check valve becomes highly viscous, and thus, the surface is likely to stick to the wall. Thus, the bending state of the flexible portion sticking at the abnormal position may not be restored. Also, when the check valve sticks at the abnormal position similar to a suction cup, the bending state of the flexible portion may not be restored.
If the flexible portion sticks at the abnormal position as described above, the function of the piezoelectric pump may be stopped. Also, if the flexible portion sticks at the abnormal position and closes the channel, a fluid pressure from the outside may exceed a withstanding pressure, possibly resulting in the piezoelectric pump being broken.